1) Field of the Disclosure
The disclosure relates to air conditioning systems, and more particularly, to electrically driven air conditioning systems for aircraft that do not rely on engine and auxiliary power unit (APU) bleed air.
2) Description of Related Art
Known air conditioning systems used in transport aircraft typically use an air-to-air thermodynamic cycle to provide cool air to various interior compartments of the aircraft, such as the passenger cabin, cargo holds, and other interior compartments. During ground operations, such air conditioning systems may operate with the use of electric and pneumatic power from main aircraft engines and/or on-board auxiliary power units (APUs). Air from the compressor stages of the main aircraft engines and/or the on-board APUs, such air also known as “bleed air”, may typically be output at a high temperature and a high pressure. Such bleed air may then be cooled and conditioned through air conditioning packs of the air conditioning system. Air conditioning packs may comprise integrated assemblies of air turbines, compressors, fans, heat exchangers, ducts, valves, and other mechanical components. Once the bleed air is conditioned in the air conditioning packs, it may then be distributed into the aircraft interior for aircraft interior temperature control, ventilation, and pressurization. The conditioned air within the aircraft interior may then be discharged to the outside ambient environment through various overboard valves, overflow valves and cabin leaks. However, extracting energy from the main engines and APUs in the form of bleed air can reduce the efficiency of the main engines and APUs and can result in increased fuel consumption and load on the main engines and APUs. Bleed air can require a significant amount of fuel burn where a significant amount of energy can be wasted by the processing of the bleed air.
Other known air conditioning systems for aircraft include electric based air conditioning systems that do not use bleed air. Similar to bleed air based systems, an electric based air conditioning system and its associated power generation and distribution equipment must be sized to accommodate worst case operating conditions, such as a hot weather ground operation. The size and weight of the air conditioning equipment and related power generation and distribution equipment can impact the overall weight of the aircraft and its fuel consumption.
Other known electric based air conditioning systems for aircraft include those disclosed in U.S. Pat. No. 6,526,775 (“Electric Air Conditioning System for an Aircraft”) and U.S. Pat. No. 7,207,521 (“Electric-Based Secondary Power System Architectures for Aircraft”). However, such known air conditioning systems draw their air source strictly from the outside ambient environment. As is the case with known air conditioning systems, the size, weight, complexity, and energy usage of the air conditioning system is typically derived from the need to cool and dehumidify warm, humid outside air to a temperature and humidity that meets the cooling needs of the aircraft interior.
Accordingly, there is a need for an aircraft system and method for improved ground cooling efficiency that provides advantages over known systems.